MgFe2O4 microspheres having a 20-32 mu m diameter range were prepared by a spray dryer using bead-milled nano-sized particles. A commercial powder having a several mu m particle size was bead-milled to an approximate 6.2 nm crystallite size. The microspheres were obtained using the spray dryer when the air pressure was low (0.03 MPa). The yield of the MgFe2O4 20-32 mu m microspheres was improved by combination of a low air pressure and high ferrite concentration in the slurry. The heat generation ability in an AC magnetic field (370 kHz, 1.77 kA/m) was improved by the bead milling. (C) 2010 The Ceramic Society of Japan. All rights reserved.